I would have already done it. But since its also driven by two others at home, so the tank is filled randomly and hence the calculation has not been possible.
But from my experience with 2014+ honda models (Vezel, Civic-rebirth, BRV) - especially the brv, the computer calculated trip average is usually +/- 10% of the actual.
So if its showing 14.1, the top-up method at worst would give around 13 (but that isn't always the case). I've found that these newer ECUs report pretty accurate figures.